Synthesis and crystal structures of thermally stable titanocenes

Article abstract of DOI:10.1016/S0022-328X(02)01726-6

Reduction of fully substituted titanocene dichlorides SiMe₂CH₂CH₂Ph, 3; SiMe₂Ph, 4; and SiMePh₂, 5) with magnesium in THF proceeds via the formation of titanocene monochlorides [TiCl (η⁵-C<

Full text of DOI:10.1016/S0022-328X(02)01726-6

Journal of Organometallic Chemistry 663 (2002) 134ꢂ144
/
www.elsevier.com/locate/jorganchem
Synthesis and crystal structures of thermally stable titanocenes
a
Lenka Lukesˇova´ , Michal Hora´cˇek , Petr Steˇpnicˇka , Karla Fejfarova´ ,
a
b
b
ˇ
Ro´bert Gyepes b, Ivana C´ısarˇova´ b, Jirˇ´ı Kubisˇta a, Karel Mach a,ꢀ
a J. Heyrovsky´ Institute of Physical Chemistry, Academy of Sciences of the Czech Republic, Dolejsˇkova 3, 182 23 Prague 8, Czech Republic
b Department of Inorganic Chemistry, Charles University, Hlavova 2030, 128 40 Prague 2, Czech Republic
Received 28 May 2002; accepted 18 July 2002
Dedicated to Professor Pascual Royo on the occassion of his 65th birthday in recognition of his outstanding contributions to organometallic
chemistry
Abstract
Reduction of fully substituted titanocene dichlorides [TiCl2(h5-C5Me4R)2] (Rꢁ
5) with magnesium in THF proceeds via the formation of titanocene monochlorides [TiCl(h5-C5Me4R)2] 6ꢂ
titanocenes, [Ti(h5-C5Me4R)2], 9ꢂ
11. Titanocene monochlorides give the expected EPR spectra in toluene solution and glass. The
structure of 7 was further corroborated by single-crystal X-ray diffraction. Titanocenes 9ꢂ11 are EPR silent down to ꢃ196 8C but
exhibit paramagnetic broadening of the signals in solution NMR spectra. The positions of the NMR signals are temperature-
dependent, obeying the Curie Law in the range investigated (0ꢂ60 8C). As revealed by X-ray crystallography, titanocenes 9 and 11
possess bent metallocene structures with the cyclopentadienyl rings tilted at an angle of 9.8(1) and 14.4(2)8, respectively. Titanocenes
9ꢂ11 are easily oxidized with PbCl2 to the parent dichloride complexes 3ꢂ5. Titanocenes 9 and 10 react with bis(trimethylsil-
yl)ethyne (btmse) only in large excess of the alkyne to give an equilibrium concentration of the respective [Ti(h5-C5Me4R)2(h2-
CSiMe3)] complexes. On the other hand, titanocene 11 does not observably react with btmse.
/SiMe2CH2CH2Ph, 3; SiMe2Ph, 4; and SiMePh2,
/
8 to afford monomeric
/
/
/
/
/
/
Me3SiCꢀ
/
# 2002 Elsevier Science B.V. All rights reserved.
Keywords: Titanium; Titanocenes; Bent titanocenes; Silyl substituents; X-ray crystallography
1. Introduction
lated cyclopentadienyl ligands [3]. The coordination-
stabilized titanocene [(m-N2){Ti(h5-C5Me4H)2}2] readily
eliminates dinitrogen and, subsequently, dihydrogen to
Electron-deficient, monomeric titanocenes are ther-
mally unstable due to their strong tendency to acquire
more valence electrons by means of various rearrange-
ments which generally result in a conversion of Ti(II) to
Ti(III) or Ti(IV) [1]. Accordingly, the parent titanocene,
[Ti(h5-C5H5)2], rearranges to green ‘dimeric titanocene’,
give a paramagnetic dimer with bridging Tiꢁ
CCp s-
/
bonds [{Ti(h1:h5-C5Me4)(h5-C5Me4H)}2] [4]. Even the
relatively stable decamethyltitanocene, prepared by an
elimination of dinitrogen from [(m-N2){Ti(h5-
C5Me5)2}2], is inherently contaminated by hydride
species [TiH(h5-C5Me5)(h1:h5-C5Me4CH2)] [5]. Thus,
so far only silicon-modified fully ring-substituted tita-
[(mꢂ
h5:h5-C5H4C5H4){Ti(m-H)(h5-C5H5)}2], very ra-
/
pidly under ambient conditions [2]. Thermal stability
of methyl-substituted titanocenes increases with the
number of electron donating methyl groups on the
cyclopentadienyl ligands; however, compounds analo-
gous to dimeric titanocene are obtained from transiently
formed titanocenes containing mono- up to trimethy-
nocenes [Ti(h5-C5Me4SiMe2R)2] (Rꢁ
/
But 1 [6] or Me 2
[7]) were found to be stable at ambient temperature.
Titanocene 1 resulted from the reduction of [TiCl(h5-
C5Me4SiMe2But)2] with sodium amalgam [6]. An ana-
logous reduction of [TiCl2{h5-C5Me4(SiMe3)}2] with
magnesium metal is complicated by side reactions [8]
and, hence, compound 2 was obtained alternatively by
thermolysis of bis(trimethylsilyl)ethyne (btmse) complex
[Ti{h5-C5Me4(SiMe3)}2(h2-btmse)] [7]. Here, we report
ꢀ Corresponding author. Tel.:
86582307
E-mail address: mach@jh-inst.cas.cz (K. Mach).
ꢄ
/
420-2-66053735; fax:
ꢄ/420-2-
0022-328X/02/$ - see front matter # 2002 Elsevier Science B.V. All rights reserved.
PII: S 0 0 2 2 - 3 2 8 X ( 0 2 ) 0 1 7 2 6 - 6

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L. Lukesˇova et al. / Journal of Organometallic Chemistry 663 (2002) 134ꢂ
/
144
135
the synthesis and crystal structures of thermally stable
titanocenes containing other silyl substituents on other-
wise fully methylated cyclopentadienyl ligands.
2. Results and discussion
2.1. Synthesis of ring-silylated titanocene dichlorides 3ꢂ
/
5
Cyclopentadienes C5HMe4(SiMe2CH2CH2Ph),
C5HMe4(SiMe2Ph), and C5HMe4(SiMePh2) were ob-
tained in good yields from the metathesis of lithium
tetramethylcyclopentadienide with commercially avail-
able chlorosilanes ClSiMe2CH2CH2Ph, ClSiMe2Ph, and
ClSiMePh2, respectively. Their 1H- and 13C-NMR
spectra revealed the presence of only one double-bond
isomer with the silicon group attached to the C-sp3 ring-
carbon atom. The synthesis of titanocene dichlorides
thereof followed the procedure used for the preparation
of analogous alkenyldimethylsilyl titanocene dichlorides
[9]: in situ generated [TiCl3(THF)3] and the respective
lithium cyclopentadienide were reacted to give Ti(III)
intermediates, which were without isolation oxidized
with AgCl to titanocene dichlorides [TiCl2(h5-
Scheme 1.
minor loss of the chlorine atom, thus resembling the
behaviour of [TiCl{h5-C5Me4(SiMe3)}2] [13].
The monochloride d1 complexes are paramagnetic,
showing in toluene solution EPR spectra consist of one
broad single line whose g-factor decreases in the order 6
(1.959), 7 (1.950), and 8 (1.948). In keeping with a
growing anisotropy of the high-field g-tensor compo-
nent (g3) in toluene glass [10], the linewidth (DHpp)
increases in the same order. The g-factor values for 7
and 8 belong amongst the lowest ones reported for fully
substituted titanocene monochlorides (cf. [11]). Com-
C5Me4R)2] (Rꢁ/SiMe2CH2CH2Ph, 3; SiMe2Ph, 4; and
SiMePh2, 5) in 16ꢂ
/
28% isolated yields. Compounds 3ꢂ5
/
were characterized by NMR, IR, and EI-MS spectra.
The latter showed an elimination of one cyclopentadie-
nyl ligand as the major fragmentation process with the
elimination of chloride ligand being less abundant.
Molecular ion was observed in neither case.
pounds 6ꢂ8 display very similar EPR spectra in both
/
THF and toluene solutions. This proves an absence of
the solvent coordination; otherwise the EPR signal of
2.2. Preparation and properties of titanocene
8
THF-adducts should occur at gꢁ1.979 [10]. In the
/
monochlorides 6ꢂ
/
presence of active magnesium the complexes are reduced
both in the presence and the absence of btmse to the
Reduction of titanocene dichlorides 3ꢂ
/
5 by half molar
respective titanocenes 9ꢂ11 (see below).
/
equivalent of activated magnesium in THF affords the
corresponding titanocene monochlorides, [TiCl(h5-
C5Me4R)2], 6ꢂ
/
8 in high yields (Scheme 1). When all
2.3. Crystal structure of 7
the magnesium was consumed the product 6 was
worked-up by extraction with hexane whereas com-
pounds 7 and 8, due to their low solubility in hexane,
were extracted and crystallized from toluene. Crystalline
8 obtained in this manner is contaminated by the formed
MgCl2 which is also slightly soluble in toluene. Com-
pounds 6 and 7 form blue solutions in both THF and
toluene, while the solutions of 8 are turquoise. Electro-
Compound 7 crystallizes with the symmetry of C2/c
space group, so that the crystallographic twofold axis
passes through the titanium and chlorine atoms what
makes only one-half of the molecule crystallographically
independent. The molecular structure of 7 (Fig. 1)
corroborates the pseudotrigonal coordination around
the titanium atom. Its molecular parameters (Table 1)
do not differ markedly from those found for the closely
related [TiCl{h5-C5Me4(SiMe3)}2] [13]. The cyclopenta-
dienyl rings are in a staggered conformation, and a steric
congestion induced by the bulky silyl groups is largely
relieved by their placement in side positions on the
nic absorption spectra of 6ꢂ
the same appearance, showing an absorption band at
550ꢂ570 nm accompanied by a broad shoulder at 650ꢂ
670 nm. These bands of low intensity (molar extinction
coefficient ca. 1ꢅ 2a1
102) have been attributed to 1a10
transitions [12]. EI-MS spectra of 6ꢂ8 showed the silyl
/8 in toluene and THF have
/
/
/
/
/
opposite sides of the Cgꢁ
silicon substituents are directed towards the chlorine
atom forming a torsion angle (t) SiꢁCgꢁCg?ꢁSi? of
104.0(2)8. The angle subtended by the least-squares
/
Tiꢁ
/
Cg? plane (Fig. 2). The
group ions as base peaks, however, the molecular ions of
7 and 8 fragmentated with the loss of the cyclopenta-
dienyl ligands while that of 6 showed in addition a
/
/
/

´
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L. Lukesˇova et al. / Journal of Organometallic Chemistry 663 (2002) 134ꢂ144
/
Fig. 2. Structure of 7 viewed along the CgꢁCg? line.
/
MePh2)}2] (11) were obtained from reduction of titano-
cene dichlorides 3ꢂ5, respectively, with one molar
/
equivalent of activated magnesium in THF as the only
isolated products in high yields (Scheme 1). In no case,
however, the reduction leads quantitatively to titano-
cenes, and their purification is inevitable. After con-
sumption of magnesium all volatiles were evaporated
under vacuum, and the residue was extracted with
hexane. The titanocenes were purified by crystallisation
from hexane; mother liquors were separated and dis-
carded for 9 and 10 whereas all the hexane solution was
removed from 11 which is low soluble in hexane, and the
compound was re-crystallized from toluene. Even so,
EPR spectroscopy revealed the presence of trace
amounts of titanocene monochlorides (see above) and
Fig. 1. Molecular structure of 7 (30% probability ellipsoids) with the
atom numbering scheme. The non-labelled atoms are generated by the
symmetry operation (1ꢃ
/
x, y, 1/2ꢃz). For clarity, hydrogen atoms are
/
omitted.
Table 1
alkoxy derivatives, characterized by a single line at gꢁ
1.976, DHꢁ4.0 G (in toluene glass g1ꢁ1.998, g2ꢁ
1.860, g3ꢁ1.954, gavꢁ1.977). These paramagnetic im-
/
˚
Selected bond lengths (A) and bond angles (8) for 7
/
/
/
/
/
Bond lengths
a
purities were estimated to be present in less than 2% of
total titanium content. The crystalline compounds
melted at: 9, 75 8C; 10, 85 8C, and 11, 105 8C, all
without decomposition; the values may be subject of
change at eventual lower content of the above men-
tioned impurities.
TiꢁCg
2.066(2)
TiꢁCl
TiꢁC(2)
TiꢁC(4)
C(1)ꢁC(2)
C(2)ꢁC(3)
C(4)ꢁC(5)
SiꢁC(10)
SiꢁC(12)
CꢁCPh ring
2.3640(7)
2.3930(16)
2.4340(17)
1.436(2)
1.416(2)
1.419(2)
1.865(2)
1.889(2)
TiꢁC(1)
TiꢁC(3)
TiꢁC(5)
C(1)ꢁC(5)
C(3)ꢁC(4)
C(1)ꢁSi
2.3704(16)
2.3901(17)
2.3916(16)
1.436(2)
1.419(2)
1.8779(17)
1.872(2)
In C6D6 solution, compounds 9ꢂ11 show a remark-
/
SiꢁC(11)
CringꢁCMe
1
able paramagnetic broadening of H-NMR resonances,
however, no signal is observed in their EPR spectra
1.503(2)ꢂ
1.509(2)
/
1.375(3)ꢂ
/
1.400(3)
196 8C in toluene solution. In 1H-NMR
Bond angles
CgꢁTiꢁCg
down to ꢃ
spectra, titanocenes 9ꢂ
in a range ca. 0ꢂ85 ppm. Positions of the signals change
with temperature and the relative chemical shifts, Di ꢁ
dꢃd(C6D6), obey the Curie Law in the accessible
temperature range of 0ꢂ60 8C. This behaviour is similar
to that of compounds 1 and 2, and is compatible with
magnetic moments of mꢁ2.4mB determined for 1 [6] and
mꢁ2.48ꢃ
2.60mB for [Ti(h5-C5Me5)2] [5b].
Electron impact mass spectra of 9ꢂ11 show the
molecular ion [M]ꢄ of lower intensity relative to the
[Mꢃ
H]ꢄ peak which dominates a cluster of isotope and
/
b
141.4(2)
C(1)ꢁC(2)ꢁC(3) 108.64(15)
C(2)ꢁC(1)ꢁC(5) 106.34(15)
C(2)ꢁC(3)ꢁC(4) 108.22(15)
/
11 feature very broad resonances
/
C(3)ꢁC(4)ꢁC(5) 107.90(15)
C(1)ꢁC(5)ꢁC(4) 108.75(15)
c
d
/
f
36.0(1)
t
104.0(2)
/
a
Cg denotes the centroid of the C(1ꢂ/5) cyclopentadienyl ring
/
atoms; Cg? isthe centroid of the symmetry generated ring.
Symmetry transformation used to generate equivalent positions:
b
/
(1ꢃx, y, 1/2ꢃz).
Dihedral angle between the least-squares cyclopentadienyl planes.
c
/
/
d
Torsion angle SiꢁCgꢁCg?ꢁSi?.
/
planes of cyclopentadienyl rings of 36.0(1)8 is virtually
the same as in the mentioned reference compound
35.8(1)8.
/
hydrogen deficient peaks. This contrasts with spectra of
2 which are dominated by [M]ꢄ species [7] and also with
spectra of 1 where [M]ꢄ shows only 3% relative
2.4. Preparation and properties of titanocenes 9ꢂ
/
11
abundance [6]. In 9ꢂ11, the loss of hydrogen atom
/
from [M]ꢄ is the main fragmentation process leading to
a more stable methylene-containing ion. The presence of
Titanocenes [Ti{h5-C5Me4(SiMe2CH2CH2Ph)}2] (9),
[Ti{h5-C5Me4(SiMe2Ph)}2] (10), and [Ti{h5-C5Me4(Si-
neutral [MꢃH] complexes as an impurity in the bulk
/

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L. Lukesˇova et al. / Journal of Organometallic Chemistry 663 (2002) 134ꢂ
/
144
137
samples was unequivocally excluded by the absence of
any EPR signal attributable to these presumably para-
magnetic compounds. Well-defined compounds of this
type [Ti{h5-C5Me4(SiMe3)}{h1:h5-C5Me4SiMe2CH2)]
[8] and [Ti(h5-C5Me5)(h1:h5-C5Me4CH2)] [14] display
EPR spectra which would differ from EPR spectra of
the above mentioned impurities. Electronic absorption
spectra of 9ꢂ
showing the absorption band at 580ꢂ
/
11 correspond well to spectra of 1 and 2
590 nm in both
/
toluene and THF. This rules out any strong coordina-
tion of THF molecule(s) to the titanium centre.
Compounds 9 and 10 exert only a very low affinity to
btmse. Even with a 28 molar excess of btmse added to a
solution of
9
in hexane, complex [Ti{h5-
C5Me4(SiMe2CH2CH2Ph)}2(h2-btmse)] (12) formed
slowly during 2 h at 22 8C, finally reaching a concen-
tration comparable to that of unreacted 9. Similarly,
compound 10 in toluene and btmse (btmse:10ꢁ
converted to [Ti{h5-C5Me4(SiMe2Ph)}2(h2-btmse)] (13)
in 2595%. The presence of 12 and 13 was detected by
the occurrence of their electronic absorption bands at
94095 and 93595 nm, respectively, that are typical for
/20) was
/
/
/
titanocene complexes with h2-coordinated alkene and
alkyne ligands [3,7,15,16]. Complexes 12 and 13 could
not be isolated because they decomposed upon removal
of the solvent and excess btmse under vacuum at room
temperature, affording quantitatively the parent titano-
cenes. At variance, titanocene 11 in toluene did not
observably react with a similar excess of btmse. The
Fig. 3. Molecular structure of 9 (30% probability ellipsoids) showing
the atom numbering scheme. For clarity, all hydrogen atoms are
omitted.
reaction of 9ꢂ
recovered titanocene dichlorides 3ꢂ
/
11 with PbCl2 in THF [17] cleanly
5.
/
The observed low affinity of 9 and 10 towards btmse
and the absence of such an affinity for 11 contrast with
the behaviour of 2 which readily forms h2-alkyne
complex [Ti{h5-C5Me4(SiMe3)}2(h2-btmse)] stable up
to 70 8C [7]. This apparently results from a rotation
of the cyclopentadienyl ligands bearing bulky di-
methyl(phenethyl)silyl, dimethylphenylsilyl, and methyl-
diphenylsilyl substituents, sweeping up the coordination
space around the titanium centre with the effect
increasing in the above order of ligands.
2.5. Crystal structures of 9 and 11
Fig. 4. Molecular structure of 11 (30% probability ellipsoids) showing
the atom numbering scheme. For clarity, all hydrogen atoms are
omitted.
The structures of 9 and 11 were determined by single
crystal X-ray diffraction analysis. In contrast to both
structurally characterized titanocenes 1 and 2, which
showed exactly parallel cyclopentadienyl rings, com-
pounds 9 and 11 are asymmetric (Figs. 3 and 4). The
geometric parameters of both compounds are very
Cg2ꢁSi2 of 98.3(2)8 for 9 and 88.2(2)8 for 11 (see Fig.
/
5). The angle between the least-squares phenyl planes in
the molecule of 9 is 88.7(1)8. In 11, the least-squares
planes of phenyl rings at Si(1) and Si(2) atoms are
mutually rotated at different angles 84.5(1) and 71.4(1)8,
respectively. A closer inspection at the parameters of
titanocene moieties shows that the ring angle at the
carbon atom bearing the silyl group is more acute
similar (Tables 2 and 3). The Cg1ꢁ
/
Tiꢁ/Cg2 (Cg denotes
cyclopentadienyl ring centroid) angle in 9 amounts to
166.0(2) and 162.2(2)8 in 11 whilst the least-squares
cyclopentadienyl ring planes subtend an angle of 9.8(1)
and 14.4(2)8, respectively. The cyclopentadienyl ligands
are mutually rotated at the torsion angle Si1ꢁ
/
Cg1ꢁ
/

´
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L. Lukesˇova et al. / Journal of Organometallic Chemistry 663 (2002) 134ꢂ
/
144
Table 2
Table 3
˚
˚
Selected bond lengths (A) and bond angles (8) for 9
Selected bond lengths (A) and bond angles (8) for 11
Bond lengths
Bond lengths
a
a
a
a
TiꢁCg(1)
TiꢁC(1)
TiꢁC(3)
TiꢁC(5)
TiꢁC(11)
TiꢁC(13)
2.004(3)
2.325(3)
2.376(3)
2.298(3)
2.370(3)
2.334(3)
TiꢁCg(2)
TiꢁC(2)
TiꢁC(4)
TiꢁC(10)
TiꢁC(12)
TiꢁC(14)
2.001(3)
2.378(3)
2.326(3)
2.301(3)
2.379(3)
2.294(3)
TiꢁCg(1)
TiꢁC(1)
TiꢁC(3)
TiꢁC(5)
TiꢁC(11)
TiꢁC(13)
2.017(2)
2.310(2)
2.393(2)
2.330(2)
2.327(2)
2.390(2)
TiꢁCg(2)
TiꢁC(2)
TiꢁC(4)
TiꢁC(10)
TiꢁC(12)
TiꢁC(14)
2.010(2)
2.358(2)
2.381(2)
2.296(2)
2.389(2)
2.335(2)
CꢁCCp ring
1.404(5)ꢂ
1.445(4)
1.862(3)
1.854(5)
1.869(3)
1.854(5)
1.475(5)
1.471(6)
/
CringꢁCMe
1.501(5)ꢂ
1.511(5)
1.869(5)
1.887(4)
1.874(5)
1.903(4)
1.524(5)
1.535(5)
/
CꢁCCp ring
1.410(3)ꢂ
1.451(3)
1.866(2)
1.868(2)
1.881(2)
1.880(2)
/
CringꢁCMe
1.504(3)ꢂ
1.509(3)
1.862(2)
1.881(2)
1.876(2)
1.884(2)
/
Si(1)ꢁC(5)
Si(1)ꢁC(19)
Si(1)ꢁC(21)
Si(2)ꢁC(29)
Si(2)ꢁC(31)
C(22)ꢁC(23)
C(32)ꢁC(33)
C(1)ꢁSi(1)
Si(1)ꢁC(19)
Si(1)ꢁC(26)
Si(2)ꢁC(33)
CꢁCPh ring
C(10)ꢁSi(2)
Si(1)ꢁC(20)
Si(2)ꢁC(32)
Si(2)ꢁC(39)
Si(1)ꢁC(20)
Si(2)ꢁC(14)
Si(2)ꢁC(30)
C(21)ꢁC(22)
C(31)ꢁC(32)
CꢁCPh ring
1.374(4)ꢂ
1.405(3)
/
1.354(5)ꢂ
1.382(5)
/
Bond angles
a
Cg(1)ꢁTiꢁCg(2)
C(1)ꢁC(2)ꢁC(3)
C(3)ꢁC(4)ꢁC(5)
C(11)ꢁC(10)ꢁC(14) 106.1(2)
C(10)ꢁC(14)ꢁC(13) 108.0(2)
162.2(2)
108.6(2)
108.5(2)
C(2)ꢁC(1)ꢁC(5)
C(2)ꢁC(3)ꢁC(4)
C(1)ꢁC(5)ꢁC(4)
106.0(2)
108.4(2)
108.5(2)
Bond angles
a
Cg(1)ꢁTiꢁCg(2)
C(1)ꢁC(2)ꢁC(3)
C(3)ꢁC(4)ꢁC(5)
C(11)ꢁC(10)ꢁC(14) 109.3(3)
C(10)ꢁC(14)ꢁC(13) 105.6(3)
166.0(2)
108.5(3)
108.7(3)
C(2)ꢁC(1)ꢁC(5)
C(2)ꢁC(3)ꢁC(4)
C(1)ꢁC(5)ꢁC(4)
108.5(3)
108.2(3)
106.1(3)
C(11)ꢁC(12)ꢁC(13) 108.4(2)
C(12)ꢁC(13)ꢁC(14) 108.7(2)
b
C(11)ꢁC(12)ꢁC(13) 108.7(3)
C(10)ꢁC(11)ꢁC(12) 108.8(2)
f
14.4(2)
71.4(1)
c
d
C(12)ꢁC(13)ꢁC(14) 108.8(3)
v1
84.5(1)
88.8(2)
v2
b
e
C(10)ꢁC(11)ꢁC(12) 107.7(3)
f
9.8(1)
98.3(2)
t
c
d
v1
88.8(1)
t
a
Cg(1) and Cg(2) are centroids of the C(1ꢂ
/
5) and C(10ꢂ14)
/
a
Cg(1) and Cg(2) are centroids of the C(1ꢂ
/
5) and C(10ꢂ14)
/
cyclopentadienyl rings, respectively.
b
cyclopentadienyl rings, respectively.
Dihedral angle between the least-squares cyclopentadienyl planes.
Dihedral angle between the least-squares planes of phenyl rings at
b
c
Dihedral angle between the least-squares cyclopentadienyl planes.
Dihedral angle between the least-squares planes of phenyl rings.
Torsion angle Si(1)ꢁCg(1)ꢁCg(2)ꢁSi(2).
c
Si(1) atom.
d
d
Dihedral angle between the least-squares planes of phenyl rings at
Si(2) atom.
e
Torsion angle Si(1)ꢁCg(1)ꢁCg(2)ꢁSi(2).
(106.1(3) and 105.6(3)8 for 9; 106.0(2) and 106.1(2)8 for
11) compared to analogous angles at other ring carbon
atoms (107.7(3)ꢂ109.3(3)8). This appears to be a general
/
feature of silyl-substituted permethylated cyclopentadie-
nyltitanium compounds since a similar cyclopentadienyl
ring angles were also found for symmetric titanocene 2
[7], monochloride 7 (106.3(2)8) as well as for eight
titanocene complexes bearing h5-C5Me4SiMe2R with R
being a methylene linked to a bridging ansa-chain or to
a titanacycle [9]. The least-squares cyclopentadienyl ring
planes are nearly perpendicular to the Tiꢁ/Cg vectors,
and maximum deviations of the Si atoms from the least-
squares planes of cyclopentadienyl rings in outward
˚
direction (0.194(4) A for Si(2) of 11) are comparable
with analogous maximum deviations of methyl carbon
Fig. 5. A view of structure of 11 along the Cg(1)ꢁCg(2) direction.
/
3. Conclusions
˚
atoms (0.182(4) A for C(6) of 11). It shows that bulky
In addition to so far known thermally stable titano-
cenes 1 and 2 another complexes of this type 9, 10, and
11 have been prepared. The common feature of all
thermally stable titanocenes is the presence of a bulky
silyl group on tetramethyl-substituted cyclopentadienyl
ligands. At variance with the solid-state structures of 1
and 2 which show exactly parallel cyclopentadienyl rings
substituents of the silyl groups do not impose any steric
hindrance into these titanocene molecules. The bending
of the titanocene structures and the overall asymmetry
in the solid state result most likely from crystal packing
effects induced by steric demands of the bulky silyl
groups. This corresponds to recent DFT calculations
which indicate than only a small change of the overall
energy is associated with tilting the cyclopentadienyl
rings [18].
titanocenes 9 and 11 are asymmetric and bent. The Cgꢁ
TiꢁCg angles of 166.0(2)8 for 9 and 162.2(2)8 for 11 are
much larger than typical angles of bent fully substituted
/
/

´
L. Lukesˇova et al. / Journal of Organometallic Chemistry 663 (2002) 134ꢂ
/
144
139
titanocene derivatives, e.g. [TiCl2(h5-C5Me4R)2] Rꢁ
Me, 137.4(3)8 [19], RꢁSiMe3, 137.6(5)8 [4], RꢁPh,
137.6(2)8 [11]; [TiCl(h5-C5Me4R)2] Rꢁ
Me, 143.6(2)8
[20]; RꢁSiMe3, 144.4(1)8 [4], RꢁPh, 143.4(1)8 [11];
[Ti(h5-C5Me4R)2(h2-btmse)] Rꢁ
Me, 138.6(3) [21], Rꢁ
SiMe3, 142.2(1)8 [7], and Rꢁ4-F-phenyl 138.9(1) [22].
The angles between the least-squares planes of cyclo-
pentadienyl rings f are correspondingly low: 9.8(1)8 for
9 and 14.4(2)8 for 11. Similar angles were found in
methylene-stabilized titanocene [Ti(h5-C5Me5)(h5:h1-
C5Me4CH2)] [23] and dimethylene-stabilized titanocenes
/
titanium atom due to rotating cyclopentadienyl ligands
is apparently the reason for a low stability of the
/
/
/
titanoceneꢂ/btmse complexes, decreasing in the order
/
/
of titanocenes 2ꢀ
/
9:10ꢁ11. On the other hand, the
/
/
/
/
titanium atom is accessible for chlorine atom as all these
titanocenes are oxidized by PbCl2 in THF to the
corresponding dichlorides. Investigations on thermal
/
activation of Cꢁ
/
H bonds and on oxidative addition
reactions of the silyl-containing titanocenes are in
progress.
[Ti(h5-C5Me4R){h4:h3-C5Me2(CH2)2R}] (Rꢁ
zyl) [22], and in [Ti{h5-C5Me3(CH2CH(t-Bu)CHꢂ
CHCH(t-Bu)CH2)}{h4:h3-C5Me3(CH2)2}] [24] and
/
Ph, ben-
/
4. Experimental
[Ti{h5-C5Me2Ph(CH2CH(t-Bu)CHꢂ
/CHCH(t-
4.1. Methods
Bu)CH2)}{h4:h3-C5Me2Ph(CH2)2}] [22], however, the
angles are opened on the side of the methylene groups.
Syntheses of cyclopentadienyl ligands and titanocene
These compounds are thermally stable to 150ꢂ
/
200 8C
dichlorides 3ꢂ
All manipulations with Ti(III) compounds 6ꢂ
Ti(II) compounds 9ꢂ11 were performed under vacuum
on an all-glass high vacuum line using sealed glass
devices equipped with breakable seals. 1H- (399.95
MHz) and 13C- (100.58 MHz) NMR spectra were
recorded on a Varian UNITY Inova 400 spectrometer
/
5 thereof were carried out under argon.
[22,24,25] which means that bending of their cyclopen-
tadienyl ligands does not remarkably facilitate the
activation of methyl groups on an inclined side. On
the other hand, the hydrogen abstraction from ligand to
titanium is a feasible process in permethyltitanocene [5],
the hydrogen atom is accomodated in [TiH(h5-C5Me5)2]
/8 and
/
and [TiH(h5-C5Me4Ph)2] at large Cgꢁ
/
Tiꢁ/Cg angles of
in C6D6 solutions at 25 8C. The spectra of 9ꢂ
/
11 were
152.0 and 152.38 (two molecules in unit cell) [26a] and
150.8(1)8 [26b], respectively, and structures of bent
titanocenes show that such a hydride intermediate could
be formed upon intramolecular hydrogen abstraction by
further investigated over the temperature range 0ꢂ
/
60 8C. Chemical shifts (d/ppm) are given relative to
the solvent signal (dH 7.15, dC 128.0). EI-MS spectra
were obtained on a VG-7070E mass spectrometer at 70
eV. Crystalline samples in sealed capillaries were opened
and inserted into the direct inlet under argon. EPR
spectra were recorded on an ERS-220 spectrometer
(Center for Production of Scientific Instruments, Acad-
emy of Sciences of GDR, Berlin, Germany) operated by
a CU-1 unit (Magnettech, Berlin, Germany) in the X-
band. g-Values were determined by using an Mn2ꢄ
titanium in 9ꢂ11. However, bent titanocenes 9, 10, and
/
11 melt at temperature of 75, 85, and 105 8C, respec-
tively, without observable decomposition unlike per-
methyltitanocene where the hydrogen abstraction
process occurs even at ambient temperature [5]. The
stabilizing effect of silyl groups is difficult to account for
only by electronic effects as there is apparently no direct
through space Tiꢁ
/
Si interaction at the distance of about
standard at gꢁ
temperature unit STT-3 was used for measurements in
the range ꢃ140ꢂ 25 8C. Concentrations of paramag-
netic species in samples of 9ꢂ11 were estimated by
comparison of integrated peak areas with that of a [(h5-
C5H5)2Ti(m-Cl)2Al(C2H5)Cl] standard solution (cꢁ
5.275 mM in C6H6). UVꢂnear IR spectra in the range
of 280ꢂ2000 nm were measured on a Varian Cary 17D
/
1.9860 (MIꢁ
/
ꢃ1/2 line). A variable
/
˚
3.70 A, and there is no remarkable difference in the
‘silicon effect’ resulting from replacement of silicon alkyl
substituents by phenyl groups. A steric congestion
between SiMe2 methyl groups of one cyclopentadienyl
ligand and methyl groups attached to the other cyclo-
pentadienyl ligand at the opposite position, which was
suggested to stabilize the molecule 1 with parallel
cyclopentadienyl rings does not apply to 9 where the
/
/
ꢄ
/
/
/
/
/
spectrometer in all-sealed quartz cells (Hellma). IR
spectra were measured in an air-protecting cuvette on
torsion angle Si(1)ꢁ
/
Cg(1)ꢁ
/
Cg(2)ꢁ
/
Si(2) amounts to
98.3(2)8, the silicon atoms are at a longer distance
from titanium and yet the compound is thermally stable.
Thus, the only specific effect of the silyl groups lies in
the planar deformation of the cyclopentadienyl ring
forming a more acute ring angle at the carbon atom
bearing the silicon atom (ca. 1068) and correspondingly,
all other angles of the ring are more obtuse (av. 1088). It
is difficult, however, to estimate the relevance of this
a Nicolet Avatar FTIR spectrometer in the range 400ꢂ
4000 cmꢃ1. With the exception of air-stable titanocene
dichlorides 3ꢂ5 all studied titanium compounds are
/
/
extremely air- and moisture-sensitive and therefore their
solid samples were handled in a glovebox Labmaster 130
(mBraun) under purified nitrogen. Crystalline samples
for EI-MS measurements and determination of m.p.s
were placed in glass capillaries and sealed out. KBr
pellets were prepared and placed into an air-protecting
cuvette in the glovebox.
structural change for the ease of CꢁH bond activation in
all the above titanocenes. The steric congestion at the
/

´
140
L. Lukesˇova et al. / Journal of Organometallic Chemistry 663 (2002) 134ꢂ144
/
4.2. Chemicals
36.0 mmol) in THF (50 ml) followed by a short reflux]
with lithium cyclopentadienide obtained by reacting
LiBu (30 ml of 2.5 M in hexanes, 75.0 mmol) with the
above cyclopentadiene (20.7 g, 73.0 mmol) in THF (500
ml) for 24 h at room temperature under stirring. After
refluxing this mixture for 30 h and subsequent stirring
with AgCl (5.16 g, 36.0 mmol) at 40 8C for 5 h, the
product was worked up as described for [TiCl2{h5-
C5Me4(SiMe3)}2] [13]. Yield of brown crystals of 3 was
9.8 g (42%).
The solvents THF, C6H14, and C6H5CH3 were dried
by refluxing over LiAlH4 and stored as solutions of
dimeric titanocene [(mꢂ
h5:h5-C5H4C5H4){Ti(m-H)(h5-
/
C5H5)}2] [27]. TiCl4 (International Enzymes) was pur-
ified by refluxing over copper wire and distilled in
vacuum. Butyllithium (2.5 M in C6H14, Aldrich),
1,2,3,4-tetramethylcyclopentadiene (mixture of isomers)
and chlorodimethylphenethylsilane, chlorodimethylphe-
nylsilane, and chloromethyldiphenylsilane (all Aldrich)
were transferred via syringe under Ar. Magnesium
turnings (Aldrich, purum for Grignard reactions) were
firstly used in large excess for the preparation of [Ti(h5-
C5Me5)2(h2-btmse)] [3]. Unreacted activated magnesium
was separated from the reaction mixture, washed
thoroughly with THF and stored in ampules equipped
with breakable seals. Bis(trimethylsilyl)ethyne (btmse,
Fluka) was degassed, stored as a solution of dimeric
titanocene for 4 h, and finally distributed into ampoules
by distillation on a vacuum line.
1H-NMR (C6D6): d 0.57 (s, 6H, SiMe2), 1.16ꢂ
2H, CH2Si), 1.63, 2.11 (2ꢅs1 6H, Me4C5); 2.56ꢂ
(m, 2H, CH2Ph), 7.00ꢂ
7.15 (m, 5H, Ph). 13C{1H}-
/1.25 (m
/
/2.63
/
NMR (C6D6): d 0.5 (SiMe2), 12.1, 16.9 (Me4C5); 19.9
(CH2Si), 30.8 (CH2Ph), 125.7 (Ph, CH), 127.5 (Me4C5,
Cipso), 128.4 (Ph, CH), 135.5, 137.8 (Me4C5, Cipso);
145.4 (Ph, Cipso) (one CH resonance of Ph group not
found). EI-MS (150 8C): m/z (relative abundance,%)
[684 [M]ꢄ not observed], 651 (8), 650 (9), 649 ([Mꢃ
/
Cl]ꢄ; 15), 335 (10), 334 (7), 333 (26), 332 (8), 331 (25),
284 ([Cp?ꢄ
H]ꢄ; 9), 180 (8), 179 (19), 178
/
([C5Me4SiMe2]ꢄ; 50), 177 (13), 164 (15), 163
([PhCH2CH2SiMe2]ꢄ; 88), 147 (14), 136 (10), 135
([C5Me5]ꢄ, 71), 121 (6), 119 (13), 105 (12), 91 (13), 73
(12), 60 (7), 59 ([SiMe2H]ꢄ; 100), 43 (10). IR (KBr,
cmꢃ1): 3083 (w), 3035 (w), 3027 (m), 2984 (w), 2958 (s),
2895 (vs), 1602 (m), 1494 (s), 1473 (w), 1450 (s), 1412
(m), 1375 (s), 1356 (m), 1342 (m), 1253 (s), 1243 (vs),
1166 (w), 1123 (m), 1024 (s), 948 (w), 927 (w), 910 (w),
892 (s), 878 (m), 834 (vs, b), 808 (s), 773 (s), 752 (m), 725
(m), 696 (s), 670 (w), 647 (w), 575 (vw), 558 (vw), 489
(w), 417 (s). Anal. Calc. for C38H54Cl2Si2Ti (M 685.81):
C, 66.55; H, 7.94. Found: C, 66.48; H, 7.90%.
4.3. Synthesis of 1,2,3,4-tetramethyl-5-
(dimethylphenethylsilyl)cyclopenta-1,3-diene and
titanocene dichloride (3)
1,2,3,4-Tetramethyl-5-(dimethylphenethylsilyl)cyclo-
penta-1,3-diene was obtained from 1,2,3,4-tetramethyl-
cyclopentadiene (13.8 g, 0.113 mol) by the reaction of its
lithium salt (generated from stoichiometric amounts of
1,2,3,4-tetramethylcyclopentadiene and 2.5 M LiBu)
with the equimolar amount of chlorodimethylphenethyl-
silane (22.5 g, 0.113 mol) in THF. The reaction mixture
was stirred overnight (voluminous Liꢄ(C5HMe4)ꢃ salt
largely disappeared) and the solution was reduced to
volume of ca. 30 ml by distilling off THF. After
evaporation of volatiles in vacuum the product was
distilled from oil bath (150 8C) under vacuum of a
rotary pump. Yield of yellow liquid 28.0 g (87%).
4.4. Synthesis of 1,2,3,4-tetramethyl-5-
(dimethylphenylsilyl)cyclopenta-1,3-diene and titanocene
dichloride (4)
1,2,3,4-Tetramethyl-5-(dimethylphenylsilyl)cyclo-
penta-1,3-diene was obtained from 1,2,3,4-tetramethyl-
cyclopentadiene (13.7 g, 0.113 mol) by the reaction of its
lithium salt (generated from stoichiometric amounts of
1,2,3,4-tetramethylcyclopentadiene and 2.5 M LiBu)
with the equimolar amount of chlorodimethylphenylsi-
lane (19.3 g, 0.113 mol) in THF as described above.
After evaporation of all volatiles in vacuum the product
was distilled from oil bath at 140 8C under vacuum of a
rotary pump. Yield of yellow liquid 24.2 g (84%).
1H-NMR (C6D6): d 0.16 (s, 6H, SiMe2), 1.75 (s, 12H,
1H-NMR (C6D6): d ꢃ
(m 2H, CH2Si), 1.81 (d, J :
6H, Me4C5), 2.50ꢂ2.55 (m, 2H, CH2Ph), 7.05ꢂ
5H, Ph). 13C{1H}-NMR (C6D6): d ꢃ
3.1 (SiMe2), 11.3,
/
0.02 (s, 6H, SiMe2), 0.79ꢂ
1.3 Hz, 6H, Me4C5), 1.91 (s,
7.21 (m,
/
0.84
/
/
/
/
14.7 (Me4C5); 17.1 (CH2Si), 30.6 (CH2Ph), 54.4
(C5Me4H, CH), 125.9 128.1, 128.6 (Ph, CH); 133.0,
135.7 (Me4C5, Cipso); 145.4 (Ph, Cipso). IR (neat, cmꢃ1):
3084 (w), 3062 (w), 3026 (m), 2959 (s), 2915 (vs), 2858
(s), 1631 (w), 1603 (w), 1495 (m), 1453 (s), 1410 (w), 1379
(w), 1249 (vs), 1219 (w), 1176 (m), 1123 (w), 1110 (w),
1046 (w), 1021 (w), 984 (m), 952 (w), 899 (w), 837 (vs),
772 (s), 754 (m), 725 (w), 698 (vs), 632 (w), 560 (w), 487
(m), 418 (m).
C5Me4); 2.99 (s, 1H, C5Me4H), 7.15ꢂ
/
7.43 (m, 5H, Ph).
3.8 (SiMe2), 11.3, 14.6
13C{1H}-NMR (C6D6): d ꢃ
/
(C5Me4); 54.7 (C5Me4H, CH), 127.8, 129.1 (Ph, CH);
132.8 (Ph or C5Me4, Cipso), 134.0 (Ph, CH); 135.9, 139.2
(Ph or C5Me4, Cipso). IR (neat, cmꢃ1): 3069 (m), 3050
(w), 2963 (s), 2912 (vs), 2857 (s), 1950 (vw), 1879 (vw),
1814 (vw), 1775 (vw), 1633 (w), 1590 (vw), 1487 (w),
Titanocene
dichloride
[TiCl2{(h5-C5Me4(Si-
Me2CH2CH2Ph)}2] (3) was prepared by reacting
[TiCl3(THF)3] [generated in situ by adding LiBu in
hexanes (22.5 ml of 1.6 M, 36.0 mmol) to TiCl4 (4.0 ml,

´
L. Lukesˇova et al. / Journal of Organometallic Chemistry 663 (2002) 134ꢂ
/
144
141
1442 (m), 1427 (s), 1379 (w), 1335 (vw), 1302 (w), 1248
(s), 1218 (m), 1190 (vw), 1113 (vs), 1047 (w), 1023 (w),
983 (m), 952 (w), 919 (vw), 832 (s), 817 (vs), 795 (w), 776
(m), 731 s), 700 (s), 642 (m), 559 (vw), 494 (m), 469 (w).
Titanocene dichloride [TiCl2{(h5-C5Me4(SiMe2Ph)}2]
(4) was prepared from TiCl4 (4.0 ml, 36 mmol) and
C5HMe4(SiMe2Ph) (18.6 g, 73 mmol) by the above
described procedure. Yield of brown, finely crystalline 4
4.6 g (20%).
above protocol. Yield of brown, finely crystalline 5 4.4 g
(16%).
1H-NMR (C6D6): d 1.29 (s, 3H, SiMe), 1.56, 1.95
(2ꢅ
/
s, 6H, C5Me4); 7.12ꢂ
/
7.17 (m, 6H, Ph), 7.59ꢂ7.64
/
(m, 4H, Ph). 13C{1H}-NMR (C6D6): d 0.1 (SiMe), 12.1,
17.2 (C5Me4); 127.9 (Ph, CH), 129.0 (Ph/C5Me4, Cipso),
129.1 (Ph, CH), 132.4 (Ph/C5Me4, Cipso), 136.4 (Ph,
CH), 138.6, 138.8 (Ph/C5Me4, Cipso). EI-MS (190 8C):
m/z (relative abundance, %) [752 [M]ꢄ not observed],
1H-NMR (C6D6): d 0.87 (s, 6H, SiMe2), 1.58, 2.10
719 (6), 718 (6), 717 ([Mꢃ
/
Cl]ꢄ; 9), 400 ([Mꢃ
/
Cp?ꢃ
/
(2ꢅ
/
s, 6H, C5Me4); 7.09ꢂ
/
7.45 (m, 5H, Ph). 13C{1H}-
Cl]ꢄ; 10), 395 (10), 393 (10), 318 (12), 317 ([Cp?]ꢄ;
11), 316 (7), 198 (20), 197 ([SiMePh2]ꢄ; 100), 121 (10),
105 (10). IR (KBr, cmꢃ1): 3067 (m), 3051 (m), 2997 (w),
2956 (w), 2901 (m), 1588 (w), 1567 (w), 1483 (m), 1428
(s), 1376 (m), 1335 (m), 1250 (m), 1190 (w), 1125 (w),
1105 (s), 1026 (m), 826 (w), 791 (vs), 738 (s), 715 (s), 702
(s), 669 (w), 486 (s), 481 (s), 452 (m), 438 (m). Anal.
Calc. for C44H50Cl2Si2Ti (M 753.84): C, 70.11; H, 6.69.
Found: C, 69.06; H, 6.65%.
NMR (C6D6): d 1.5 (SiMe2), 12.1, 16.9 (C5Me4H);
128.0, 128.7 (CH, Ph); 134.0 (Ph/C5Me4, Cipso), 134.3
(Ph, CH), 138.2, 141.7 (Ph/C5Me4, Cipso). EI-MS
(160 8C): m/z (relative abundance, %) [628 [M]ꢄ not
observed], 593 ([Mꢃ
(2), 373 ([Mꢃ
Cp?]ꢄ; 4), 338 ([Cp?TiCl]ꢄ; 7), 303
([Cp?Ti]ꢄ; 3), 256 (9), 255 ([Cp?]ꢄ; 6), 254 (9), 239
Me]ꢄ; 6), 176 (7), 137 (7), 136 (15), 135
/
Cl]ꢄ; 4), 558 ([Mꢃ
/
2 Cl]ꢄ; 2), 557
/
([Cp?ꢁ
/
([SiMe2Ph]ꢄ; 100), 121 (14), 120 (8), 107 (7), 105 (10),
91 (9), 73 (7), 59 (16), 57 (8), 55 (7), 44 (7), 43 (9), 43
(18), 41 (12). IR (KBr, cmꢃ1): 3067 (m), 3047 (w), 3000
(m), 2959 (m), 2901 (s), 1588 (vw), 1479 (m), 1443 (w),
1427 (m), 1407 (w), 1374 (m), 1352 (vw), 1337 (w), 1246
(s), 1124 (w), 1108 (s), 1022 (m,b), 825 (sh), 814 (vs), 774
(s), 736 (s), 702 (s), 656 (w), 475 (m), 433 (s), 406 (w).
Anal. Calc. for C34H46Cl2Si2Ti (M 629.70): C, 64.85; H,
7.36. Found: C, 64.79; H, 7.32%.
4.6. Preparation of [TiCl{h5-
C5Me4(SiMe2CH2CH2Ph)}2] (6)
The solution of 3 (1.37 g, 2.0 mmol) in THF (30 ml)
was added to activated Mg (25 mg, 1.03 mmol) and the
mixture was stirred at 60 8C until the color turned blue
and all magnesium disappeared. All volatiles were
distilled off in vacuum and the residue was extracted
with C6H14 (20 ml). The extract was concentrated to ca.
4.5. Synthesis of 1,2,3,4-tetramethyl-5-
(diphenylmethylsilyl)cyclopenta-1,3-diene and titanocene
dichloride (5)
10 ml and cooled at ꢃ18 8C overnight to afford pale
/
blue aggregates of fibrous crystals. Yield of [TiCl{h5-
C5Me4(SiMe2CH2CH2Ph)}2] (6) was 1.13 g (87%).
EPR (C6H14, 23 8C): gꢁ
(C6H5CH3, ꢃ140 8C): g1ꢁ1.9995, g2ꢁ
1.8916, gavꢁ1.958; (THF, 22 8C): gꢁ1.958, DHꢁ
/
1.959,DHꢁ
1.9822, g3ꢁ
14
/
15 G. EPR
The cyclopentadiene was obtained by the above
described procedure from 0.113 mol (26.3 g) of ClSi-
MePh2. The product distilled from oil bath at 170 8C
under vacuum of a rotary pump. Yield of viscous yellow
liquid 27.6 g (77%).1H-NMR (C6D6): d 0.35 (s, 3H,
/
/
/
/
/
/
/
G. EI-MS (170 8C): m/z (relative abundance, %) 653
(10), 652 (20), 651 (51), 650 (44), 649 ([M]ꢄ; 86), 648
(11), 647 (9), 633 ([Mꢃ
/
Me]ꢄ; 6), 614 ([MꢃCl]ꢄ; 3), 544
/
SiMe), 1.65, 1.74 (2ꢅ
C5Me4H), 7.08ꢂ
7.69 (m, 10H, Ph). 13C{1H}-NMR
(C6D6): d ꢃ6.6 (SiMe), 11.3, 14.8 (C5Me4); 53.0
/s, 6H, C5Me4); 3.39 (s, 1H,
([Mꢃ
([Mꢃ
([Mꢃ
/
Ph(CH2)2]ꢄ; 5), 451 (7), 368 (6), 367 (8), 366
/
/
Cp?]ꢄ; 14), 365 (7), 264 (7), 263 (12), 262 (23), 261
/
/
Cp?ꢃ
CH2CH2Ph]ꢄ; 20), 260 (11), 259 (12), 257
/
(C5Me4H, CH), 128.1, 128.3, 129.6, 130.1 (Ph, CH);
133.2 (Ph or C5Me4, Cipso), 134.6, 135.2 (Ph, CH);
136.8, 137.4 (Ph or C5Me4, Cipso). IR (neat, cmꢃ1): 3069
(m), 3049 (w), 3026 (vw), 3010 (w), 2997 (vw), 2959 (m),
2930 (m), 2911 (s), 2868 (w), 2855 (m), 1957 (vw), 1884
(vw), 1820 (vw), 1763 (vw), 1633 (m), 1589 (w), 1567
(vw), 1486 (w), 1442 (m), 1427 (vs), 1382 (w), 1329 (vw),
1302 (vw), 1254 (s), 1215 (m), 1192 (vw), 1169 (w), 1157
(vw), 1109 (vs), 1069 (vw), 1047 (w), 1021 (w), 998 (vw),
981 (m), 953 (w), 918 (vw), 785 (vs), 767 (m), 735 (s), 719
(m), 699 (vs), 675 (vw), 659 (vw), 562 (w), 511 (vs), 476
(m), 463 (s), 438 (w), 423 (m).
(10), 178 ([C5Me4SiMe2]ꢄ; 10), 164 (17), 163
([Ph(CH2)2SiMe2]ꢄ; 100), 135 ([C5Me5]ꢄ; 78), 73 (11),
59 (87). IR (KBr, cmꢃ1): 3100 (vw), 3082 (w), 3061 (w),
3022 (m), 2999 (m), 2953 (s), 2910 (vs), 1602 (m), 1494
(s), 1480 (m), 1453 (s), 1413 (m), 1379 (s), 1349 (w), 1332
(vs), 1253 (vs), 1178 (m), 1126 (m),1026 (s), 1003 (w),
909 (w), 899 (m), 835 (vs), 809 (vs), 768 (s), 751 (m), 719
(m), 697 (s), 643 (w), 561 (w), 492 (w), 423 (s). UVꢂ
/vis
(C6H5CH3, 22 8C, nm): 555ꢁ670 (sh) nm.
/
4.7. Preparation of [TiCl{(h5-C5Me4(SiMe2Ph)}2] (7)
Titanocene dichloride [TiCl2{(h5-C5Me4(SiMePh)2}2]
(5) was prepared from TiCl4 (4.0 ml, 36 mmol) and
C5HMe4(SiMePh2) (23.2 g, 73 mmol) according to the
Compound 4 (0.5 g, 0.8 mmol) and magnesium
turnings (10.0 mg, 0.42 mmol) were placed into an
ampoule, evacuated on a vacuum line, and THF (20 ml)

´
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L. Lukesˇova et al. / Journal of Organometallic Chemistry 663 (2002) 134ꢂ
/
144
was distilled in. The solution of 4 was then heated to
60 8C until all the magnesium disappeared (5 days). The
solvent was distilled off, the residue was washed with 10
ml of C6H14 and dissolved in 30 ml of C6H5CH3. The
solvent was then slowly distilled from one ampoule into
another leaving blue crystalline material over white layer
of MgCl2. This residue was then extracted by conden-
sing vapour of C6H5CH3 to leave majority of MgCl2 on
an ampoule wall. The saturated toluene solution
afforded turquoise crystals of 7 for EI-MS, IR, and
m.p. measurements and for X-ray single crystal analysis.
the mixture was stirred at 60 8C until the color turned
turquoise and all magnesium disappeared (after 1ꢂ3
/
days). Then, all volatiles were distilled off under vacuum
and the residue was extracted with C6H14. Partial
solvent removal and cooling to ꢃ18 8C overnight
/
gave 9 as grey prisms. Yield: 1.02 g (83%).
M.p. 75 8C. EI-MS (160 8C): m/z (relative abun-
dance, %) 616 (9), 615 (31), 614 ([M]ꢄ; 50), 613 ([Mꢃ
/
H]ꢄ; 100), 612 (14), 611 (13), 509 ([MꢃPh(CH2)2]ꢄ; 8),
/
445 (5), 331 ([Mꢃ
Cp?]ꢄ; 10), 163 ([PhCH2CH2SiMe2]ꢄ;
/
5), 135 ([C5Me5]ꢄ; 9), 59 (21). IR (KBr, cmꢃ1): 3082
(w), 3059 (w), 3025 (m), 2951 (s), 2907 (vs), 1602 (m),
1494 (s), 1452 (s), 1379 (m), 1332 (m), 1315 (s), 1246 (vs),
1166 (m), 1130 (m), 1021 (s), 894 (s), 832 (vs), 801 (s),
The reduction of 4ꢂ7 proceeded apparently quantita-
/
tively but only the first partial crop of crystals (0.080 g)
was isolated and used for characterization.
EPR (C6H5CH3, 22 8C): gꢁ
(C6H5CH3, ꢃ140 8C): g1ꢁ1.999, g2ꢁ
1.856, gavꢁ1.945; (THF, 22 8C): gꢁ1.949, DHꢁ
/
1.950, DHꢁ
1.981, g3ꢁ
17
/
17 G;
764 (s), 751 (m), 697 (s), 445 (m). UVꢂ
22 8C, nm): 590.
/
vis (C6H14,
/
/
/
/
/
/
/
G. EI-MS (180 8C): m/z (relative abundance, %) 597
4.10. Preparation of [Ti{(h5-C5Me4(SiMe2Ph)}2] (10)
(8), 596 (19), 595 (43), 594 (42), 593 ([M]ꢄ; 76), 592 (11),
591 (8), 578 ([Mꢃ
339 (39), 338 ([Mꢃ
/
Me]ꢄ; 6), 577 (9), 341 (10), 340 (33),
Complex 10 was obtained from 1.25 g (2.0 mmol) of 4
and 2.0 mmol of activated magnesium as described for
9. A concentrated C6H14 extract afforded a crystalline
/
Cp?]ꢄ; 76), 337 (48), 336 (12), 322
(8), 136 (14), 135 ([SiMe2Ph]ꢄ; 100), 121 (9), 59 (10), 43
(10). IR (KBr, cmꢃ1): 3063 (m), 3048 (w), 2995 (m),
2957 (s), 2904 (s), 1959 (vw), 1944 (vw), 1888 (vw), 1873
(vw), 1809 (vw), 1759 (vw), 1588 (vw), 1566 (vw), 1484
(w), 1450 (w), 1427 (m), 1410 (w), 1379 (m), 1334 (m),
1243 (s), 1187 (vw), 1157 (vw), 1126 (w), 1106 (s), 1065
(vw), 1023 (m), 998 (vw), 835 (s), 821 (s), 808 (vs), 774
(m), 753 (w), 727 (s), 699 (s), 655 (m), 572 (vw), 542 (vw),
yellowish green product by cooling to ꢃ18 8C. A
/
yellow mother liquor was separated and discarded,
and the product was recrystallized from C6H14. Yield
of grey crystalline material was 0.56 g (50%).
M.p. 85 8C. EI-MS (160 8C): m/z (relative abun-
dance, %) 560 (9), 559 (28), 558 ([M]ꢄ; 57), 557 ([Mꢃ
/
H]ꢄ; 100), 556 (41), 555 (15), 304 (13), 303 ([MꢃCp?]ꢄ;
/
471 (m), 447 (s), 424 (s). UVꢂ
/
vis (C6H5CH3, 22 8C,
40), 302 (19), 301 (11), 136 (10), 135 ([SiMe2Ph]ꢄ; 67),
73 (29), 59 (10). IR (KBr, cmꢃ1): 3065 (m), 3051 (m),
2952 (s), 2912 (vs), 2860 (m), 1971 (w), 1896 (vw), 1880
(vw), 1819 (vw), 1765 (vw), 1588 (vw), 1567 (vw), 1485
(w), 1450 (w), 1427 (s), 1410 (w), 1379 (m), 1328 (m),
1314 (m), 1246 (s), 1188 (vw), 1129 (m), 1107 (s), 1065
(vw), 1022 (m), 998 (vw), 830 (sh), 822 (sh), 811 (vs), 769
m), 727 (s), 701 (s), 656 (m), 580 (w), 514 (w), 469 (m),
nm): 568ꢁ670 (sh).
/
4.8. Preparation of [TiCl{(h5-C5Me4(SiMePh2)}2] (8)
Compound 5 (0.5 g, 0.66 mmol) and magnesium
turnings (8,0 mg, 0.33 mmol) were reacted in THF as
described for 7. Dark green crystalline product was
obtained by crystallization from hot C6H5CH3 solution.
Only the first crop of crystals was used for characteriza-
tion as further crops should contain more MgCl2 which
is also soluble in C6H5CH3 (although much less than 8).
Yield of crystalline 8 0.13 g (18%).
436 (s). UVꢂvis (C6H5CH3, 22 8C, nm): 580.
/
4.11. Preparation of [Ti{(h5-C5Me4(SiMePh2)}2] (11)
Complex 11 was obtained from 5 (1.50 g, 2.0 mmol)
and acitivated magnesium as for 9 and 10. The residue
after evaporation of THF in high vacuum was repeat-
edly extracted by C6H14 in order to separate the low-
soluble product from MgCl2. The concentrated C6H14
solution was poured away from a residue, and this was
EPR (C6H5CH3, 22 8C): gꢁ
(C6H5CH3, ꢃ140 8C): g1ꢁ1.998, g2ꢁ
1.850, gavꢁ1.943; (THF, 22 8C): gꢁ1.947, DHꢁ
/
1.948, DHꢁ
1.980, g3ꢁ
21
/
20.0 G;
/
/
/
/
/
/
/
G. EI-MS (250 8C): m/z (relative abundance, %) 721
(9), 720 (21), 719 (41), 718 (44), 717 ([M]ꢄ; 66), 716 (11),
715 (8), 485 (9), 403 (11), 402 (34), 401 (36), 400 ([Mꢃ
Cp?]ꢄ; 75), 399 (29), 398 (10), 198 (20), 197
([SiMePh2]ꢄ; 100), 121 (13), 105 (14), 91 (10). UVꢂ
vis
(C6H5CH3, 22 8C, nm): 575ꢁ680 (sh).
/
dissolved in toluene to give a yellowꢂ
Greenish brown prism crystals were obtained by cooling
the concentrated solution to ꢃ18 8C. Yield: 1.0 g
(73%).
M.p. 105 8C. EI-MS (190 8C): m/z (relative abun-
dance, %) 683 (8), 682 ([M]ꢄ; 16), 681 ([MꢃH]ꢄ; 26),
/
green solution.
/
/
/
4.9. Preparation of titanocene 9
/
680 ([Mꢃ
/
2H]ꢄ; 31), 679 (6), 365 ([MꢃCp?]ꢄ; 7), 364
/
Complex 3 (1.37 g, 2.0 mmol) in THF (30 ml) was
added to activated magnesium (50 mg, 2.06 mmol) and
(6), 318 ([Cp?H]ꢄ; 9), 199 (9), 198 (20), 197
([SiMePh2]ꢄ; 100), 121 (6), 105 (9). IR (KBr, cmꢃ1):

´
L. Lukesˇova et al. / Journal of Organometallic Chemistry 663 (2002) 134ꢂ
/
144
143
Table 4
Crystal and structure refinement data for 7, 9 and 11
Compound
7
9
11
Chemical formula
C34H46ClSi2Ti
594.24
150(2)
C38H54Si2Ti
614.88
293(2)
C44H50Si2Ti
682.92
150(2)
MW (g molꢃ1
T (K)
Crystal system
)
Monoclinic
C2/c (No. 15)
19.5550(7)
11.9460(4)
14.5450(5)
90
Triclinic
¯
Triclinic
¯
P1 (No. 2)
Space group
˚
/
P1/(No. 2)
/
a (A)
˚
10.010(1)
13.583(2)
14.550(2)
104.46(1)
95.32(1)
105.46(1)
1819.3(4)
2
10.0770(3)
11.6870(4)
17.1540(4)
70.777(2)
82.920(2)
80.470(2)
1876.1(1)
2
b (A)
˚
c (A)
a (8)
b (8)
g (8)
V (A )
Z
Dcalc (g cmꢃ3
111.263(2)
90
3
˚
3166.5(2)
4
1.247
)
1.121
0.324
1.209
0.322
m(Moꢂ
/
Ka) (mmꢃ1
)
0.452
1268
F(000)
662
Grey
728
Brown
Crystal colour
Crystal size (mm3)
u-Range (8)
Blue
0.47ꢅ0.45ꢅ0.20
0.7ꢅ0.6ꢅ0.5
0.5ꢅ0.2ꢅ0.18
3.28ꢂ
/
27.48
1.47ꢂ
/
24.98
3.37ꢂ25.04
/
hkl range
ꢃ25/25, ꢃ15/15, ꢃ18/18
3613
ꢃ11/11, 0/16, ꢃ17/16
6375
4437
ꢃ11/11, ꢃ13/13, ꢃ19/20
6520
Unique diffractions
Observed diffractions
Parameters
R(F), wR(F2) (all data)
R(F), wR(F2) (observed diffractions)
a
2871
179
5566
434
382
b
0.0521, 0.0927
0.0370, 0.0856
1.031
0.0906, 0.1652
0.0535, 0.1459
1.041
0.0523, 0.1088
0.0420, 0.1021
1.039
b
c
S (all data)
ꢃ3
˚
(Dr)max, (Dr)min, (e A
)
0.313, ꢃ0.270
0.618, ꢃ0.257
0.473, ꢃ0.418
a
Diffractions with Ioꢁ2s(Io).
R(F)ꢁa jjFojjꢃjjFojj/a jFoj, wR(F2)ꢁ[a (w(Fo2 ꢃFc2)2)=a w(Fo2)2]1=2
:/
b
c
Sꢁ
/
[a (w(Fo2 ꢃFc2)2)=(Ndiffractions ꢃNparemeters)]1=2
:/
3065 (m), 3046 (m), 2993 (w), 2955 (s), 2910 (vs), 2858
(m), 1971 (w), 1882 (vw), 1820 (vw), 1766 (vw), 1587 (w),
1566 (w), 1485 (m), 1427 (vs), 1381 (m), 1310 (m), 1249
(m), 1187 (w), 1128 (w), 1107 (vs), 1066 (vw), 1023 (m),
998 (w), 818 (m), 787 (vs), 737 (s), 714 (s), 700 (vs), 670
Compound 10 (0.12 g, 0.22 mmol) in 4.0 ml of
C6H5CH3 was reacted with 1.0 ml of btmse
(btmse:Tiꢁ
/
20) for 2 h and UVꢂnear IR spectra were
/
measured. A new absorption band of 13 at 930 nm
occurred while the band at 580 nm due to 10 diminished.
A final estimate molar fraction of 13 in the 10/13
(m), 493 (s), 471 (m), 456 (m). UVꢂ
/
vis (C6H5CH3,
22 8C, nm): 590.
mixture was 2595%. Twice repeated evaporation of
/
volatiles followed by dissolution of the residue in C6H14
afforded a solution showing only the band at 580 nm.
Analogous experiment of 11 with btmse in C6H5CH3 did
4.12. Reaction of 9ꢂ11 with btmse
/
not result in occurring any band in the region 800ꢂ
nm.
/
1200
Btmse (1.0 ml, 4.47 mmol) was added to a solution of
9 (0.10 g, 0.16 mmol; molar ratio btmse:Tiꢁ28.0) in
C6H5CH3 (4.0 ml). An absorption band at 940 nm in
UVꢂnear IR spectrum of the mixture occurred and grew
/
/
4.13. Oxidation of 9ꢂ11 with PbCl2
/
in intensity during 1.5 h while, simultaneously, the band
due to 9 at 590 nm showed a moderate decrease and its
maximum moved to 620 nm as a result of increasing
background absorption at shorter wavelengths. After 2
h the intensity ratio did not change further. Attempted
isolation of [Ti{(h5-C5Me4(SiMe2CH2CH2Ph)}2(h2-
btmse)] (12) by evaporation of all volatiles under
vacuum and redissolution of the residue in C6H14 (4.0
ml) lead to a complete recovery of 9 as indicated by
Crystalline 9 (0.21 g, 0.34 mmol) was dissolved in
THF (20 ml) and the solution was poured on vacuum-
dried, solid PbCl2 (0.095 g, 0.34 mmol). The mixture was
stirred at 60 8C for 4 h while the colour changed to
reddish brown. Volatiles were evaporated in vacuum,
and the residue was extracted with C6H14 (20 ml). The
solution was concentrated to crystallisation and cooled
overnight to ꢃ18 8C. Crystalline 3 (0.20 g, 87%) was
/
UVꢂ
/
near IR spectrum. Replacement of C6H14 with
THF did not change the spectrum either.
identified by EI-MS and 1H- and 13C-NMR spectra.
Analogous reactions of 10 (0.20 g, 0.36 mmol) and 11

´
144
L. Lukesˇova et al. / Journal of Organometallic Chemistry 663 (2002) 134ꢂ144
/
[4] J.M. De Wolf, R. Blaauw, A. Meetsma, J.H. Teuben, R. Gyepes,
V. Varga, K. Mach, N. Veldman, A.L. Spek, Organometallics 15
(1996) 4977.
(0.20 g, 0.32 mmol) with equimolar amounts of PbCl2 in
THF afforded 4 (0.18 g, 79%) and 5 (0.20 g, 84%),
respectively.
[5] (a) J.E. Bercaw, R.H. Marvich, L.G. Bell, H.H. Brintzinger, J.
Am. Chem. Soc. 94 (1972) 1219;
4.14. X-ray crystallography
(b) J.E. Bercaw, J. Am. Chem. Soc. 96 (1974) 5087.
[6] P.B. Hitchcock, F.M. Kerton, G.A. Lawless, J. Am. Chem. Soc.
120 (1998) 10264.
Fragments of a blue crystal of 7, a grey prism of 9,
and a brown platelet of 11 were inserted into Lindemann
glass capillaries in a glove box. Diffraction data for 9
ˇ
[7] M. Hora´cˇek, V. Kupfer, U. Thewalt, P. .Steˇpnicˇka, M. Pola´sˇek,
K. Mach, Organometallics 18 (1999) 3572.
[8] M. Hora´cˇek, J. Hiller, U. Thewalt, M. Pola´sˇek, K. Mach,
Organometallics 16 (1997) 4185.
were collected on an EnrafꢂNonius four-circle CAD4
/
ˇ
[9] L. Lukesˇova´, P. .Steˇpnicˇka, K. Fejfarova´, R. Gyepes, I. C´ısarˇova´,
and the data for 7 and 11 on a Nonius KappaCCD
diffractometers. The structures were solved by direct
methods (SIR-92, [28]) and refined by weighted full-
matrix least-squares on F2
(SHELXL-97, [29]). All non
hydrogen atoms were refined with anisotropic thermal
motion parameters. The hydrogen atoms were included
in calculated positions. Relevant crystallographic data
are given in Table 4.
M. Hora´cˇek, J. Kubisˇta, K. Mach, Organometallics 21 (2002)
2639.
[10] K. Mach, J.B. Raynor, J. Chem. Soc. Dalton Trans. (1992) 683.
[11] M. Hora´cˇek, M. Pola´sˇek, V. Kupfer, U. Thewalt, K. Mach,
Collect. Czech. Chem. Commun. 64 (1999) 61.
[12] W.W. Lukens, R.M. Smith, III, R.A. Andersen, J. Am. Chem.
Soc. 118 (1996) 1719.
[13] M. Hora´cˇek, R. Gyepes, I. C´ısarˇova´, M. Pola´sˇek, V. Varga, K.
Mach, Collect. Czech. Chem. Commun. 61 (1996) 1307.
[14] T. Vondra´k, K. Mach, V. Varga, A. Terpstra, J. Organomet.
Chem. 425 (1992) 27.
ˇ
[15] P. .Steˇpnicˇka, R. Gyepes, I. C´ısarˇova´, M. Hora´cˇek, J. Kubisˇta, K.
5. Supplementary materials
Mach, Organometallics 18 (1999) 4869.
[16] P.-M. Pellny, V.V. Burlakov, W. Baumann, A. Spannenberg, M.
Crystallographic data for the structural analysis have
been deposited at the Cambridge Crystallographic Data
Centre, CCDC nos. 186411, 173171, 186443 for com-
pounds 7, 9 and 11. Copies of this information may be
obtained free of charge from The Director, CCDC, 12
ˇ
Hora´cˇek, P. .Steˇpnicˇka, K. Mach, U. Rosenthal, Organometallics
19 (2000) 2816.
[17] G.A. Luinstra, J.H. Teuben, Chem. Commun. (1990) 1470.
[18] J.C. Green, Chem. Soc. Rev. 27 (1998) 263.
[19] T.C. McKenzie, R.D. Sanner, J.E. Bercaw, J. Organomet. Chem.
102 (1975) 457.
Union Road, Cambridge CB2 1EZ, UK (Fax: ꢄ44-
/
[20] J.W. Pattiasina, H.J. Heeres, F. van Bolhuis, A. Meetsma, J.H.
Teuben, A.L. Spek, Organometallics 6 (1987) 1004.
[21] V.V. Burlakov, A.V. Polyakov, A.I. Yanovsky, Yu.T. Struchkov,
1223-336033; e-mail: deposit@ccdc.cam.ac.uk or www:
http://www.ccdc.cam.ac.uk).
V.B. Shur, M.E. Vol’pin, U. Rosenthal, H. Gorls, J. Organomet.
¨
Chem. 476 (1994) 197.
ˇ
[22] V. Kupfer, U. Thewalt, I. Tisˇlerova´, P. .Steˇpnicˇka, R. Gyepes, J.
Acknowledgements
Kubisˇta, M. Hora´cˇek, K. Mach, J. Organomet. Chem. 620 (2001)
39.
[23] J.M. Fischer, W.E. Piers, V.G. Young, Organometallics 15 (1996)
2410.
Financial support of Grant Agency of the Czech
Republic (projects No. 203/02/0774 and No. 203/99/
M037) is gratefully acknowledged.
ˇ
[24] M. Hora´cˇek, P. .Steˇpnicˇka, R. Gyepes, I. C´ısarˇova´, M. Pola´sˇek,
K. Mach, P.-M. Pellny, V.V. Burlakov, W. Baumann, A.
Spannenber, U. Rosenthal, J. Am. Chem. Soc. 121 (1999) 10638.
[25] J.W. Pattiasina, C.E. Hissink, J.L. de Boer, A. Meetsma, J.H.
Teuben, A.L. Spek, J. Am. Chem. Soc. 107 (1985) 7758.
[26] (a) W.W. Lukens, Jr., P.T. Matsunaga, R.A. Andersen, Organo-
metallics 17 (1998) 5240;
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¨